Models Definition and 369 Threads

Hey guy, I'm working at my school to ID our collection of kinematic models and make signs for explaining them. I have them almost done, but there are a few I can't find in any of the books, can you guys take a look at the attached and linked pictures and see if you can ID them?

Hello everyone, haven't been here in a while. My tutor asked me wether I wouldn't be interested in writing a smal program to illustrate one particular case of 3-body problem. I definitely would be, it's just that I've never written any application displaying anything. Numerical calculations...

It surprises me how much mathematics is needed to solve the innocent-looking 2D Ising model, and the Heisenberg model is quite an exercise even in 1D. I begin to doubt whether solving these models is really worth the effort, given that these systems don't look very realistic, and computer...

For my coursework, i am investigating the angle of repose of granular materials. However, for my coursework to be. . . successful i need to prove or disprove a theory or an empirical equation which i can test. So far from my research i have not found a simple... or appropriate complexity theory...

In what aspect do they fail (IKKT and BFSS) to be?

In analog models of gravity, such as http://en.wikipedia.org/wiki/Acoustic_metric" , the motion of "matter" is influenced by the metric. Detection of Hawking radiation in sonic black holes is a goal that some experimental groups are working on. However, in GR geometry and matter act on each...

hi there, i am looking for the site about sharing 3D models, (like 3dcadbrowser) if you know, can you help me?

Hi all I'm a complete newbie to the subject of electricity and trying to wrap my head round it. To be more precise, I'm trying to build a mental model for myself that accurately predicts what goes on in circuits. I've read several accounts that suggest a model based on the flow of...

Suppose the LHC discovers that EW is dynamically broken by technicolor, topcolor, top quark condensate models. Can these be harmonized with SUSY? If new strongly interacting dyanmics breaks EW, how would that modify SUSY, including SUSY particle content? Or, would discovery of technicolor/top...

Hi all, I'm doing some test prep for a Nuclear Physics course and working on a past paper. I've attached a photo of the question. The diagram is 3.19 in Krane. The course is based on Krane, and so the relevant chapter is Chp 5: Nuclear Models. Problem description The problem is to explain...

Which of the common cosmological models do you prefer and why? Assume we don't know which if any of the models is the actual one that matches the universe.

Assuming inflation is true, we have this paper by Guth, Valenkin and Borde: http://cdsweb.cern.ch/record/521154 which says that inflation can't be past eternal and then we have this paper saying it can be made past eternal: http://arxiv.org/abs/gr-qc/0301042 Can anyone explain to me the...

While I know next to nothing about the philosophy of science, I would think about scientific models and explore whether there are features of these models that should be required in order to say they make a good theory or whether any model that predicts the data is as good as any other. From...

Homework Statement An Archer on top of a 50-ft high cliff shoots a 4-oz arrow straight up in the air. The bow is strung so that it can achieve maximum initial velocity of 128 feet per second. If the air resistance causes a drag constant of 1/1024 lb/fps, what is the maximum elevation reached...

Homework Statement A 500-gallon tank originally contains 350 gallons of pure water. A 2-pound per gallon brine solution is pumped into the tank at 10 gallons per minute and the well-stirred mixture is pumped out at one-half that rate. How much salt is in the tank at th emoment of overflow...

Working on some DE homework and need a tad bit of guidance. I got fairly far, I'm just wondering what the next step is. Homework Statement The rate of change of an alligator population P is proportional to the square of P. The swamp contained a dozen alligators in 1988, two dozen in 1998...

Hi there, I have a question regarding thermodynamics in the expanding universe. I'm specifically looking at section 7.1 of Galaxy Formation by Malcolm S. Longair. In this section, he sets out to show that the dynamical equations for the scale factor automatically incorporate the first law of...

Hopefully you don't mind me saying this, I get the impression PhysicsForums is trying to tell me to turn my mind into a vegetable because all thoughts/feelings are automatically found in a book no matter what and so you have to purge all your feelings. I wonder if coming up with some...

I have a question for those who are cognisant with the study of economics. I've heard in economic classes they teach all sorts of mathematical models to describe/predict all the "laws" in the field, or at least approximations. I'm trying to hunt down the popular and useful economics...

Hello, I'm creating a slide-show presentation that describes how a shape charge explosion (namely that of an improvised explosive formed projectile) is more effective than that of a bullet projectile. I would like to include visuals and equations which describe how the initial explosion...

Been enjoying Physics Forums and this is my first question so before I ask I should I applaud everyone for the helpful friendly atmosphere. I'm trying to understand the concepts of continuity and connectedness. I have no set theory background nor physics backgrounds so I just read online...

This is a follow up to my previous question, as they appear that in both the Godel Metric and the Van Stockum dust Perhaps a better way to put this is, could there be a model where you had rotation (maybe around a non-symmetrical axis?) and not get these CTCs?

Is there a general approach to calculating the impact outliers have on the accuracy of one's (predictive) model?

Is there a finite model of ZF - Infinity?

In case anyone wants to comment, I thought I'd start a thread on it. http://arxiv.org/abs/0908.3683 Early Universe models from Noncommutative Geometry Matilde Marcolli (Caltech), Elena Pierpaoli (USC) 49 pages, 26 figures (Submitted on 25 Aug 2009) "We investigate cosmological predictions on...

I am currently preparing for a few wind tunnel tests on a NACA 2412 airfoil. The lab technician told me that before I can use the tunnel, I need to provide solid proof that the models will be able to hold up in the wind tunnel (up to speeds of 110 mph (30 psf)). In the technician's own words...

Homework Statement According to classical physics, a charge e moving with an acceleration a radiates at a rate dE/dt = - (e2a2)/(6pi epsilon c3) a) Show that an electron in a classical hydrogen atom spirals into the nucleus at a rate dr/dt = - e4/ (12pi^2 epsilon^2 r^2 me^2c3) b) Find...

I've never really understood how electron taking the form of a standing wave in the orbit of a nucleus can have particle characteristics (ex. momentum based on the formula p = h/lambda). Also I could never grasp with the idea of something being both a particle and a wave at the same time and...

I like to play and abuse RC car models like this: However, when making big jumps or high-speed crashes (they can even reach 90mph), even steel parts gets damaged and needs to be substituted. See these damaged/broken parts for example: http://img169.imageshack.us/img169/4286/cimg1700.jpg...

I know that answers to the following can sometimes be subjective and biased... but still... What are the most 'promising' models in string theory, judged by the potential realization of a realistic SS standard model? Also, in particular, how do Intersecting Brane Models (since their...

When using the Friedmann equation (flat space, no cosmological constant): H = sqrt (8 pi G / 3 ) * rho, if we use rho in mass/volume, H is in (time)^-1 like it should. Now for some inflation models, we use: H = sqrt (8 pi G / 3 ) * V(Phi). It seems that V(Phi) should also be able to be...

Following are some descriptions of Inflationary Model(s) of the Universe which are quite different than I have read elsewhere. My own view, I now believe, was likely a bit myopic. These comments reflect Paul Steinhardt and Neil Turoks' descriptions in their book ENDLESS UNIVERSE where they...

Hello. I use P-Spice student version and I regret that standard librairies offer very few number of models, especially for Op-Amp's. Is there sites where I can download more components models.

1. Homework Statement The transient behaviour of a capacitor has been studied by measuring the voltage from across the device as a function of time. The following data has been obtained. Time (s)/Voltage (v) 0 / 10 1 / 6.1 2 / 3.7 3 / 2.2 4 / 1.4 5 / 0.8 6 / 0.5 7 / 0.3 8 / 0.2 9...

1) "Simple linear regression model: Y = β0 + β1X + ε E(Y) = β0 + β1X A linear model means that it is linear in β's, and not necessarily a linear function of X. The independent variable X could be W2 or ln(W), and so on, for some other independent variable W." I have some trouble...

1) "Simple linear regression model: Yi = β0 + β1Xi + εi , i=1,...,n where n is the number of data points, εi is random error We want to estimate β0 and β1 based on our observed data. The estimates of β0 and β1 are denoted by b0 and b1, respectively." I don't understand the difference...

1) "In regression models, there are two types of variables: X = independent variable Y = dependent variable Y is modeled as random. X is sometimes modeled as random and sometimes it has fixed value for each observation." I don't understand the meaning of the last line. When is X random...

Hello, I'm a student from Lithuania. I have found in one forum topic your discussion about non-linear equation convertion into a linear form.. I have some problem with that...Could you help me, please? :) For, example, I have two non-linear models: 1. y = a [1/(1+b/(c+x))]*exp(-d*x) 2. y =...

In my high school Honors Chemistry course today, we performed a simulation (along with several real labs) of chemical (dynamic) equilibriums. I'll briefly outline the simulation: 1. Place 42 pennies on the reactants side and 0 on the products side. 2. In the first round, move 1/3 of the...

Homework Statement The radius of the orbit of an electron in a hydrogen atom is 0.05 nm. Using the planetary model, calculate the orbital velocity needed by the electron to avoid being pulled into the nucleus by electrostatic attraction. Round up your answer to the nearest tenth...

Can someone explain what's Z2 symmetry ? Is it necessary to have it in a model, even SM ?

This video is worth watching. http://pirsa.org/08120001/ Quantum Nature of the Big bang in Simple Models. Abhay Ashtekar Perimeter video with slides PDF 3 December 2008 "According to general relativity, space-time ends at singularities and classical physics just stops. In particular, the big...

1. Given Information/Objectives The following system for "stable competition": dx/dt=(2-2x-y)x dy/dt=(2-x-2y)y Find the equilibrium points for the system. Using the Jacobian matrix, linearize the system about the equilibrium that has both species present. Classify this equilibrium...

Hello, I am studing polytropes and I found something intersting here: http://astronomy.sussex.ac.uk/~pd48/Polytropes.ppt I got a problem at slide 5 where she says that the polytropic index n is equal to 0 for a homogenous gas sphere. I am not able to figure out why. From the polytropic...

A rocket is fired vertically and ascends with constant acceleration a=100m/s^2 for 1min. At that point, the rocket motor shuts off and the rocket continues upward under the influence of gravity. a) Find the maximum altitude acquired by the rocket b) The total time elapsed from the...

I'm wondering if anyone is aware of any computational/theoretical work on solving the problem of describing the motion of a biological macromolecule in a cellular microdomain? This would have to mean setting up and solving a stochastic partial differential equation with boundary conditions...

I'm looking at different topics for my masters thesis and one of them that has a lot of potential is a heat transfer model for a piston in an internal combustion engine. Apparently the auto industry has never directly addressed this problem and use a trial and error method when it comes to...

What are the acceptable models to eplain how the big bang is expanding the space of our visible universe? Are these the choices? 1) An expanding infinity 2) local expansion with an area of non-expansion beyond our range of observation 3) local expansion with an an area of non expansion in...

http://www.alexisparkinn.com/weird_aviation_videos.htm scroll down to bottom of page for video. Are these models? impressive looking.

I am taking a project this year. As the title suggests this project is a maths project but I was wondering if anyone can direct me to some science field in which I could use stochastic models. I have very limited knowladge in science so something theoretical would be nice. Any books would be...